Evaluation of bean (Phaseolus vulgaris) seeds' inoculation with Rhizobium phaseoli and plant growth promoting rhizobacteria (PGPR) on yield and yield components.

Growing evidence indicates that soil beneficial bacteria can positively affect symbiotic performance of rhizobia. The effect of co-inoculation with plant growth-promoting rhizobacteria (PGPR) and Rhizobium, on yield and yield components of common bean (Phaseolus vulgaris L.) cultivars was investigated in two consecutive years under field condition. PGPR strains Pseudomonas fluorescens P-93 and Azospirillum lipoferum S-21 as well as two highly effectiveRhizobium strains were used in this study. Common bean seeds of three cultivars were inoculated with Rhizobium singly or in a combination with PGPR to evaluate their effect on growth characters. A significant variation of plant growth in response to inoculation with Rhizobium strains was observed. Treatment with PGPR significantly increased pod per plant, number of seeds per pod, weight of 100 seed, weight of seeds per plant, weight of pods per plant, total dry matter in R6 as well as seed yield and protein content. Co-inoculation with Rhizobium and PGPR demonstrated a significant increase in the yield and yield components. The results showed that all treatments of bacteria increased yield; however, strains Rb-133 with P. fluorescens P-93 gave the highest seed yield, number of pods per plant, weight of 100 seed, seed protein yield, number of seed per pod, and seed protein yield.   Key words: Bean seeds, Rhizobacteria, yield component, plant growth.